1. Field of the Invention
This invention relates to a battery pack having a rechargeable secondary battery housed within a battery casing. More particularly, it relates to a battery pack employed for supplying power to portable electronic equipment, such as a portable video camera unit.
2. Description of the Related Art
There is extensively employed a so-called handy-type video camera unit which is able to record moving pictures easily on, for example, an eight mm wide video tape. Since this handy type video camera is lightweight, small-sized and can be transported easily, a battery pack having a so-called secondary battery housed therein is typically used as a power source.
A conventional battery pack, as shown for example in FIG. 1, is made up of a substantially rectangular battery casing 50, first to fifth rechargeable secondary batteries 51a to 51e accommodated in the battery casing 50, an anodic plate 52 connected to an anode of the first secondary battery 51a for use as an anode terminal, and a cathodic plate 53 connected to the cathode of the fifth secondary battery 51e for use as a cathode terminal.
The battery casing 50 has a substantially planar junction surface 50a by which the battery casing is to be connected to a power supply surface of a video camera unit or a charger. On the junction surface 50a are formed a cavity for anodic terminal 54 and a cavity for cathodic terminal 55 at a predetermined interval from each other. Within these cavities 54 and 55, which are preferably elliptical in shape, the anodic plate 52 and the cathodic plate 53 are provided for closing them from the back side of the junction surface 50a.
The first to fifth secondary batteries 51a to 51e are substantially cylindrical in shape and are each of a length slightly shorter than the transverse width of the battery casing 50. The secondary batteries 51a to 51e are transversely arrayed in the battery casing 50 so that the anodes and the cathodes are alternately directed in the opposite directions, as shown by broken lines in FIG. 1. Within the battery casing 50, the first secondary battery 51a has its cathode connected to the anode of the second secondary battery 5lb by a connecting plate (not shown), the second secondary battery 5lb has its cathode connected to the anode of the third secondary battery 51c by a connecting plate 56, the third secondary battery 51c has its cathode connected to the anode of the fourth secondary battery 51d by a connecting plate (not shown), and the fourth secondary battery 51d has its cathode connected to the anode of the fifth secondary battery 51e by a connecting plate 57. That is, the first to fifth secondary batteries 51a to 51e are connected in series with one another so that the anode of the first secondary battery 51a is connected to the anodic plate 52 and the cathode of the fifth secondary battery 51e is connected to the cathodic plate 53.
Meanwhile, the upper surface 50b of the battery casing 50 opposite to the junction surface 50a has its four corners 50c rounded to facilitate handling because these corners are caused to abut on the palm of the hand of the user when connecting the battery pack to the power supply surface of the video camera unit or the charger.
The power supply surface of the video camera unit or the charger is provided with an anode contacting pin and a cathode contacting pin which are contacted at their upper ends with the anodic plate 52 and the cathodic plate 53, respectively, when the power supply surface is connected to the junction surface 50a of the battery pack.
During charging, there are stored in the battery pack the electrical energies supplied from the charger by way of the anode contacting pin, cathode contacting pin, anodic plate 52 and the cathodic plate 53 in this order. Conversely, during discharging, the electrical energies stored in the battery pack by charging are supplied to the video camera unit by way of the anodic plate 52, cathodic plate 53, anode contacting pin and the cathode contacting pin in this order.
With the above-described battery pack, since the special mounting space is provided in the junction surface 50a for the anodic terminal and the cathodic terminal, that is, the anodic plate 52 and the cathodic plate 53, the battery pack itself is increased in size in an amount corresponding to the mounting space for the anodic and cathodic terminals to retrogress from the goal of reducing the size of the video camera unit.
On the other hand, since the anodic terminal and the cathodic terminal are plate-shaped and contacted by the upper ends of the anodic contact pin and the cathodic contact pin provided on the charger or on the video camera unit for charging or discharging electrical energies, the anodic contact pin or the cathodic contact pin cannot be contacted reliably with the anodic terminal or with the cathodic terminal, respectively, thus leading to contact troubles. Besides, since the plate-shaped surface is contacted with the contact pins, the battery pack cannot be supported reliably by the charger or by the video camera unit, thus leading to wobbling of the battery pack during use or to the battery pack being detached from the charger or from the video camera unit.